Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 20, 1950 UNHTED STATES PATENT OFFHE ANTIOXIDANTS FOR MINERAL OIL LUBRI- OANTS AND COMPOSITIONS CONTAINING THE SAME No Drawing.

Application June 25, 1948,

Serial No. 35,284

13 Claims. 1

This invention relates to antioxidants for mineral oil lubricants and compositions containing the same, and more particularly, it relates to addition agents for mineral oil lubricants which inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is due at least in part to oxidation effects on mineral lubricating oils. In turbine oils, the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubricants which will inhibit the oxidative deterioration of such lubricants.

It is further an object of this invention to provide improved mineral oil lubricant compositions which are remarkably stable against oxidation under service conditions.

: added to mineral oil lubricants, confers a rem'arkable stability against deterioration by oxidation. Such condensation products and mineral oil lubricant compositions containing them are believed to be novel and are considered parts of our invention. Contrary to what may be expected from the nature of the reactants, we do not obtain highly-condensed, insoluble resinous products.

- On the contrary, when the above reactants are condensed in accordance with our invention, t ere are obtained light-colored condensation products which are non-resinous and which are readily soluble in mineral oils.

In performing the condensation the reactants are mixed and heated to a maximum temperature of 350 F. We have found that if a temperature of 350 F. is exceeded to any substantial extent, the condensation product formed tends to be resinous and insoluble. The temperature for the condensation usually ranges from -350 F., however, the preferred temperature therefor ranges from 320 F. The proportions of the reactants may vary somewhat. The methyl ether of amylphenol may be employed in an amount of from 1 to 2 mols; N-dimethylaniline may be employed in an amount of from 1 to 2 mols; and the amount of formaldehyde may range from lto 2 mols per mol of the methyl ether of amylphenol. Ordinarily, it is preferred to use from 5 to 10 per cent by weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as 1 per cent by weight, and larger amounts, as high as 20 per cent by weight may also be employed; but larger amounts than about 10 per cent by weight are ordinarily not necessary.

In lieu of formaldehyde any formaldehydeyielding compound, such as paraformaldehyde, dioxymethylene and trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term formaldehyde is intended to include formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clay catalysts may be employed in accordance with our invention. Such materials are well known in the art and comprise a natural clay, such as bentonite, fullers earth, fioridin and smectite, which has been acid treated in order to activate the clay. These materials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agent, the reactants and catalysts are, placed into a reaction vessel which is then closed and the mixture heated with agitation until all of the formaldehyde or formaldehyde-yielding compound has been consumed. At this time the water which is formed as a result of the condensation is removed, preferably under vacuum, and the dehydrated condensation product is then filtered to remove the activated clay catalyst. In some instances, it is desirable to prepare our new addition agent in a concentrate in a mineral lubricating oil which ma then be diluted down with additional oil to the concentration desired in the final lubricating composition. In such instances, the mineral lubricating oil may be added in a 8 suitable amount, say in a weight equal to the weight of reactants, to the reaction mixture in the reaction vessel, and the condensation product obtained will then be a concentrated solution of the addition agent in the mineral lubricating oil.

The condensation products obtained in accordance with our invention are liquids or crystalline solids. While we do not desire to be bound by any theory as to the reaction or reactions involved or the chemical composition of the products, we-believe that in view of the multiple points of the respective molecules at which the reactants may react, we obtain a mixture of chemical compounds" The exact nature of the manner in which the catalyst influences the reaction is unknown. However, regardless of any theory involved, the use of an activated clay catalyst is an essential feature of our invention, since if the'catalyst is omitted, black, insoluble, resinous condensation'products are obtained.

The following examples illustrate the preparation of our new addition agent:

Example I.-Into an iron reaction vessel were charged 178 pounds (1 pound mol) of methyl ether of amylphenol, 242 pounds (2 pound mols) of N-dimethylaniline, and 160 pounds of 37% by weight aqueous formaldehyde (2 pound mols of anhydrous formaldehyde) along with 40 pounds of Filtrol (an activated clay) as a catalyst. The mixture was refluxed and agitated at 210 F. for a period of 12 hours, and then the temperature was raised to 280 F. and all water, both that added with the formaldehyde andformed in the reaction, was distilled on. The product was then filtered and had the following properties;

Gravity, API 6.3 Color, NPA 4.0 Neutralization No. 1.7

Example II.Into an iron reaction vessel were charged 178 pounds (1 pound mol) of methyl of Filtrol as a catalyst. The mixture was refluxed and agitated at 210 F. for a period of 12 hours, and then the temperature was raised to 280 F. and all water, both that added with the formaldehyde and formed in the reaction, was distilled ofi. The filtered product had the following properties:

Gravity, "API 5.1 Color, NPA 4.0 Neutralization No. 2.9

The condensation products obtained in accordance with the above disclosure from methyl ether of amylphenol, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst are excellent addition agents for mineral oil lubricants. They are readily soluble in all types of mineral oils, that is, parafiinic, naphthenic or mixed base mineral oils in high proportions to form concentrated solutions thereof, which may then be diluted down to the proportions desired in the final mineral oil lubricant composition. As stated, our new addition agents are remarkably efi'ective in inhibiting the oxidative deterioration of mineral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally sumcient. For example, our addition agents may be added to mineral lubricating oils or greases in minor amounts, say from 0.001 to 1 per centby weight 4 of the mineral oil or grease, suiiicient to inhibit the oxidative deterioration of the oil or grease. Larger amounts of our new addition agents may be used if desired, but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant effects of our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subjected to a, standard oxidation test which measures the stability of the oils to oxidation. The oxidation test referred to is a standard test described in ASTM Standards on Petroleum Products and Lubricants," September, 1943, pages 17-20. Briefly, the test comprises subjecting the oil sample to oxygen at a temperature of C. (203 F.) in the presence of water and an ironcopper catalyst, and determining the time required to build up a neutralization number of 2. The flow of oxygen is maintained at 3 liters per hour. The remarkably effective stability to oxidation of mineral oil lubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example Ills-An improved motor lubricating oil was prepared by treating an SAE 30 base motor stock with 0.5% by weight of the antioxidant prepared according to Example I. A comparison of the properties of the base oil and the improved oil showed:

Example IV.An improved steam turbine oil was prepared by treating a turbine 011 base with 0.5% by weight of the antioxidant prepared according to Example I. A comparison of the properties of the base oil and the improved oil showed:

Base Improved Oil Oil Gravity, API 28. 6 28. 4 Oxidation Test:

ASTM-Proposed- 203 F., 3 L.. Oxygen/Hr:

Time Oxidized, Hr 1m 2, 500 Neutralization No 2. 0 2. 0

Example V.An improved steam turbine oil was prepared by treating a turbine oil base with 0.5% by weight of the antioxidant prepared according to Example II. A comparison of the properties of the base oil and improved oil showed:

The above examples show the remarkable oxidation stability imparted to mineral oil lubricant compositions by the use of our new addition agents. Mineral oil lubricant compositions containing our new addition agents are therefore eminently suited for use where the operating conditions are extremely severe, as in Diesel, tank and truck engines, and in the lubrication of steam turbines.

The remarkable effects of our new addition agents cannot be readily accounted for and cannot be predicted from the nature of the reactants. Thus, condensation products prepared from other functionally similar compounds have been found to be either prooxidant or to show no antioxidant efiects whatsoever. For example, we have prepared a condensation product similar to our new addition agent by substituting aniline for N- dimethylaniline. The resulting condensation product was found to be entirely unsuitable for inhibiting the oxidative deterioration of mineral oil lubricant compositions.

Other known addition agents may be incorporated into the lubricant compositions prepared in accordance with our invention. pour point depressants, extreme-pressure agents, bearing corrosion inhibitors and the like may be added.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which'comprises heating from 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol in the presence of an activated clay catalyst at a temperature not in excess of 350 F. to condense together the three reactants, and recovering the condensation product.

2. The process of preparing an addition agent for mineral-oil lubricants which comprises heating from 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethyl aniline and l to 2 mols of formaldehyde per mol of methyl ether of amylphenol in the presence of 5 to per cent by weight of the total reactants of an activated clay catalyst at a temperature of from 150 to 350 F. to condense together the three reactants, and recovering the condensation product.

condense together the three reactants, and re-- For example,

3. The process of preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol in the presence of 5 to 10 per cent by weight of the total reactants of an activated clay catalyst at a temperature of from 190 to 320 F. to condense together the three reactans, and recovering the condensation product.

4. The process of preparing an addition agent for mineral oil lubricants which comprises adding an activated clay catalyst, from 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol to a mineral lubricating oil, heating the mixture to a temperature not in excess of 350 F. to form a condensation product of the three reactants, and recovering a solution of. the condensation product in the mineral lubricating oil.

5. The'process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol oi methyl ether of amylphenol, 2 mols of N-dimethylaniline, and 2 mols of formaldehyde in the presence of an activated clay catalyst at a temperature or from 190, to 320 F. to

covering the condensation product.

'7. A non-resinous condensation product of from 1 to 2 mols'of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol, saidproduct being obtained by the process of claim l.

8. A non-resinous condensation product of 1 mol of methyl ether of amylphenol, 2 mols of.

N-dimethylaniline and 2 mols of formaldehyde, said' product being obtained by the process of claim 5. 7 v

9. A non-resinous condensation product of 1 mol of methyl ether of amylphenol, 1 mol of N-dimethylaniline, and 2 mols of formaldehyde, said product being obtained by the process of claim 6.

10. A lubricant composition comprising a major amount of a mineral lubricating oil, and

aminor amount, suflicient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of from 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol, said product being obtained by the process of claim 3.

11. A lubricant composition comprising a major amount of a mineral lubricating oi1,'and a'minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a non-resinous condensation product of 1 to 2 mols of methyl ether of amylphenol with from 1 to 2 mols of N-dimethylaniline and 1 to 2 mols of formaldehyde per mol of methyl ether of amylphenol, said product being obtained by the process of claim 1.

12. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suflicient to inhibit the oxidative deterioration of said 011 of a non-resinous condensation product of 1 mol of methyl ether of amylphenol, 2 mols of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process of claim 5.

13. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor, amount, sufllcient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 mol of methyl ether of amylphenol, 1 mol of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process or claim 6.

HERSCHEL G. SMITH. TROY L. CANTRELL. JOHN G. PETERS.

REFERENCES CITED The following references are of record in th flleot this patent:

UNITED STATES PATENTS Number Name Date 1,594,983 Sommerville Aug. 3, 1920 2,097,162 Musselman Oct. 26, 1997 2,113,599 Musselman Apr. 12, 1938 2,281,401 Wilson Apr. 28. 1942 2,431,011 Zimmer Nov. 18, 199'! Certificate of Correction Patent N 0. 2,512,444 June 20, 1950 HERSCHEL G. SMITH ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 57, for reactans read reactants; column 6, line 36, for the claim reference numeral 3 read 1;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammissz'oner of Patents.

Patent N 0. 2,512,444

Certificate of Correction June 20, 1950 HERSCHEL G. SMITH ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 57, for reactans read reactants; column 6, line 36, for the claim reference numeral 3 read 1;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gomnz'aaioner of Patents. 

4. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTS WHICH COMPRISES ADDING AN ACTIVATED CLAY CATALYST, FROM 1 TO 2 MOLS OF METHYL ETHER OF AMYLPHENOL WITH FROM 1 TO 2 MOLS OF N-DIMETHYLANILINE AND 1 TO 2 MOLS OF FORMALDEHYDE PER MOL OF METHYL ETHER OF AMYLPHENOL TO A MINERAL LUBRICATING OIL, HEATING THE MIXTURE TO A TEMPERATUR NOT IN EXCESS OF 350* F. TO FORM A CONDENSATION PRODUCT OF THE THREE REACTANTS, AND RECOVERING A SOLUTION OF THE CONDENSATION PRODUCT IN THE MINERAL LUBRICATING OIL. 